A memory using a ferroelectric material, e.g., a ferroelectric random access memory (FERAM) is a nonvolatile memory which stores data based upon the direction of polarization of the ferroelectric material. In a ferroelectric memory, for example, a memory cell includes a ferroelectric capacitor and a switching transistor. The stored data is read out by applying a voltage to the ferroelectric capacitor in such a manner that the polarization is oriented in one direction and by determining whether the polarization at this moment is inverted or not. Such a ferroelectric memory is disclosed in, for example, IEEE International Solid-State Circuits Conference, DIGEST OF TECHNICAL PAPERS, 1994, pp. 268-269.
In ordinary operation, on the other hand, the ferroelectric memory may be used as a dynamic random access memory (DRAM) by fixing a plate potential of the ferroelectric capacitor to, for example, a power source voltage. When the power source is turned off, however, the operation is performed, in which the data of the stored potential is converted into data of the direction of polarization of the ferroelectric material. This makes it possible to hold the data even after the power source is turned off. Such a ferroelectric memory is disclosed in, for example, Symposium on VLSI Technology, DIGEST OF TECHNICAL PAPERS, 1990, pp. 15-16.